This invention relates to video imaging systems for viewing objects on a video display and more particularly to a system for measuring various parameters of the object being viewed.
In video image display systems such as borescopes and endoscopes for viewing inaccessible remote objects, unless the distance from the lens to the object and hence the magnification is known or a known scale is placed next to the object, accurate measurement of features of the object is impossible. In co-pending application Ser. No. 364,883, filed June 12, 1989, now U.S. Pat. No. 4,980,763 dated Dec. 25, 1990 assigned to the common assignee of the present case, and which application is specifically incorporated herein by reference; there is disclosed a system for providing object distance or magnification information concerning the object being viewed. In said application a supplementary image of known position or size is projected on the object being viewed with the object illumination and then knowing the parameters of the image system the object distance (magnification) is calculated according to the size or position of the supplementary image. Once the object distance is known, the object can be measured by reference to a calibrated scale or the like on the video display. In the referenced application it was also suggested that certain of the measurement functions could be accomplished by counting pixels on the video display screen.
In many applications, particularly in the industrial and medical fields, additional information over and above that provided by a simple two dimensional video display is required. Also, instantaneous real time information is frequently needed. Thus, in addition to the linear dimension of an object, the depth or thickness, positional orientation, surface configuration, etc., are frequently required and these details are frequently needed with great precision.
The present invention provides pixel by pixel calibration and distortion correction to image measurements and also provides a significant amount of three dimensional information about the object being viewed.